Causes

There are a great many things that have been blamed for causing varicose veins - almost all of them are complete nonsense. However the commonest are outlined in the first section below:
 
Q1 “Crossing your legs causes varicose veins”

A.

It is often stated that if you cross your legs you can get varicose veins. Sometimes nurses and doctors will tell patients in hospital that if they cross their legs they will get a deep vein thrombosis (DVT).
 
The thinking behind this statement seems to be the idea that the veins need to be straight to let blood flow up them properly, and that crossing the legs could either kink the veins or put pressure on the veins causing them to close. It is this kinking of the veins or the pressure put on the outside of the veins that seems to be blamed for the formation of varicose veins or deep-vein thrombosis (DVT).
 
They assume that this blocking of the vein increases the pressure of the blood inside the leg veins, making the vein walls distend and causing varicose veins further down the legs.
 
Those people who think that crossing the legs causes deep-vein thrombosis (DVT) seem to think that the blockage of the veins by them kinking or external pressure causes the blood to stop flowing and therefore to clot. A blood clot in these deep veins of the legs is indeed a deep vein thrombosis (DVT).
 
However, crossing the legs does not cause either of these venous conditions.
 
We will look first at the idea of crossing the legs leading to the formation of varicose veins. Even if this action did cause a kink or put external pressure on a vein, this would not lead to an increase of pressure within the veins but would cause the vein to block off. A blocked vein has stationary blood in it. Blood only stays fluid if it keeps moving and if it stops, it clots and causes a thrombosis. Therefore if crossing the legs did cause a vein to kink or have external pressure on it, the problem would be a clot (thrombosis) not the formation of varicose veins.
 
This brings us then to the second myth, that crossing the legs can cause deep-vein thrombosis (DVT). The deep veins are shielded within muscle and they lie close the bones deep inside the leg. When the legs are crossed there is obviously contact between the legs. This contact causes pressure on the top of lower leg from the bottom of the upper leg, and pressure on the bottom of the upper leg on the top of the lower leg.
 
If the legs are crossed at the thigh, the pressure on the lower leg is on the front of the thigh. However the deep-vein at this point is behind the thigh bone (femur) and it only starts to wind around to the inside of the bone as it comes up the leg. Therefore the pressure on the lower thigh on the lower leg is not transmitted to the deep-vein. The pressure on the upper leg as it rests on the lower leg is again at the lower thigh, but at the back of the leg. At this point, there are two hamstring tendons that rest on the lower thigh, making sure that once again, no pressure is transmitted to the deep vein.
 
Similarly when the legs are crossed below the knee, pressure on the lower leg is transmitted straight onto the shin bone (tibia) or ankle bones by the upper leg. Pressure on the upper leg caused by contact with the lower leg is spread from the Achilles tendon to the bulk of the calf muscle which spreads any pressure throughout the muscle and letting very little pressure to be transmitted through to the deep calf veins.
 
Studies of flow of blood in the deep veins during sitting and crossing of legs have shown that blood flows normally in the deep veins in the normal sitting position, whether the legs are crossed or not. Due to the veins being so deep, it takes a huge pressure in a very small area to be able to have any effect on the deep veins which are protected deep inside the muscle. This sort of pressure is difficult to obtain even when we try to medically, in order to investigate the deep veins. When the legs are crossed, there is not enough pressure in a small enough area to cause the effect required to damage the deep veins.
 
Therefore crossing the legs in a normal person does not cause varicose veins or deep vein thrombosis.
 

Q2 “Pregnancy causes varicose veins”

A.

Whenever humans get a medical problem, they always look for an obvious cause. Usually, we see a medical problem in an area and instantly try to think of something that affected that area in the recent past. Once we have thought of something, we then blame that for the medical problem. A common example of this is seen when a women gets hit on the breast and then finds a breast cancer in that area. She will almost always blame the trauma as the cause of the breast cancer, even though biology will tell us that the breast cancer had been growing there for years and the fact that the breast got hit, merely drew attention to that area which caused the lump to be found.
 
Thus much research into medicine has shown that many “old wives tales” or “myths” are a failing of our understanding of how diseases develop.
 
The association of pregnancy with the formation of varicose veins is one of these cases. In the past there has been the erroneous thought that "pressure" from a baby in the womb will push on veins in the pelvis, increasing the pressure inside the veins and therefore causing varicose veins. However, an elementary knowledge of venous physiology will show this to be ridiculous.
 
If pressure is directed onto a vein from externally, the veins squashes and the flow inside it stops. There is no increase in pressure in the blood in the vein, which simply flows away from the area. However the stopping of the blood flow inside this section of vein does cause the blood to clot and cause thrombosis. Therefore, if it were true that the baby in the womb pushed directly on the veins of the pelvis, then we would see women getting massive deep-vein thrombosis (DVTs) in their pelvic veins when the foetus and womb got big enough. This is clearly not the case.
 
We know from research performed by Mark Whiteley in the 1990s that, even in our teens, we start losing valves inside our veins and start getting venous reflux or "hidden varicose veins". However when we are young, these rarely show on the surface. As time passes on, these veins get worse due to the constant backward flow of blood refluxing (or falling backwards) back down these veins the wrong way.
 
When a woman gets pregnant, she starts accumulating extra blood in her circulation. By the last three months of pregnancy, a pregnant woman has 40% more blood in her veins then in her non-pregnant state. This is approximately 1.5 to 2 litres (2 – 3 pints) of extra blood. The hormones of pregnancy cause the veins to dilate to accommodate this extra volume and, if there are any small "hidden varicose veins" that are too small to see normally just under the surface of the skin, these bulge and become distended and prominent.
 
Therefore when varicose veins appear during pregnancy, it is due to the valves in the veins having failed before pregnancy, and there will be small varicose veins already hidden away under the skin. Pregnancy just causes these veins to become swollen and more visible due to the extra volume of blood in pregnancy.
 
At the end of the 1990s, this was proven by some research performed in Chester by Miss L de Cossart in the UK. Ladies undergoing in-vitro fertilisation (IVF) were scanned before during and after their pregnancy. Thanks to the IVF, doctors knew exactly when the patient became pregnant. All patients who developed varicose veins during pregnancy were shown to have the underlying problem hidden away before they got pregnant.
 
Therefore pregnancy does not cause varicose veins, but does result in "hidden varicose veins" becoming visible due to the increase of blood volume.

Q3 “Standing for long periods of time causes varicose veins”

A.

In the 1970s and 1980s, there were quite a few research studies suggesting that people who stood for long periods of time got more varicose veins. These studies confirmed that people who stand a lot had worse varicose veins than those who didn’t stand so much. However people then made the incorrect assumption that it was the standing that caused the varicose veins. This was incorrect.

Research by Mark Whiteley from the 1990s has shown that teenagers who are susceptible to varicose veins, lose the valves in their veins as they get older. By the age of 18, one in nine 18-year-olds were found to have lost their valves and therefore have "hidden varicose veins" (venous reflux disease or venous incompetence). This meant that as they stand, blood that should be pumped back to the heart actually falls backwards down these veins, causing damage to the vein walls further down the leg, stretching the vein walls and causing varicose veins.

When people are still young and the process has only just started, the veins are strong enough to withstand this constant battering. Therefore we call this state "hidden varicose veins" as nothing can be seen on the surface, but duplex ultrasound shows us that the valves are not working and blood is refluxing the wrong way down the veins on standing. Without duplex ultrasound or another other medical test, it is impossible for anyone looking at the leg to know that are hidden varicose veins within it.

When children grow up and go to work, many of those who have hidden varicose veins will slowly start to develop visible varicose veins. The speed at which these become visible will depend upon several factors. Some will never become visible because the veins are too deep. These are the veins that will go on to cause venous eczema, skin discolouration at the ankles and leg ulcers in later life.

Those that have tributary veins closer to the surface of the skin will start to see these as varicose veins if these veins continue to dilate. Things that will cause this dilation to occur include; how many valves have been lost in the underlying veins, which veins are affected, the diameter of the veins, the strength of the vein walls and how often blood is allowed to reflux down the veins, hitting the walls of these veins and causing them to dilate.

In people who stand a lot at work, the heart is much higher than the ankles compared to someone who is sitting at work. Therefore the column of blood from heart to ankles which causes pressure on the vein walls is higher when standing, if there are no valves in the vein to interrupt this column of blood. Therefore when a person who has got hidden varicose veins stands up, a surge of blood falls down the veins, hitting the walls of these veins under the skin and starting to stretch them. The longer someone is on their feet, the more often this happens and therefore the quicker these veins are likely to dilate.

Therefore it is not standing for long periods of time that causes varicose veins. Rather if someone has already lost their valves due to their genetic make-up, then they are more likely to see varicose veins early and to develop worse varicose veins quicker if they have a job that makes them stand for long periods of time.

However people who have valves that work in their veins and who work in jobs where they have to stand for long periods of time, do not go on to get varicose veins unless the valves fail.

Simply, standing for long periods of time does not cause varicose veins, but if you already have “hidden varicose veins” then standing for long periods of time will make your varicose veins deteriorate quicker.
 

Q4 “Being overweight causes varicose veins”

A.

It has become very popular in the Western world to blame excess weight and obesity as a cause of many medical problems.

Fortunately, as far as varicose veins are concerned, there is no link between being overweight and the development of varicose veins.

In the past it has been thought that increased pressure in the abdomen from excess fat would "push" on the veins in the pelvis, increasing the pressure in the leg veins and therefore causing varicose veins.

However excess pressure on the pelvic veins does not cause extra pressure being transmitted down the blood into leg veins. Rather it pushes on the vein wall trying to close the veins. If the veins did close, the blood would clot and a deep-vein thrombosis (DVT) would be caused.

Therefore excess weight does not cause increased pressure in the veins and there is no link between weight and the development of varicose veins.
 

Q5 “Being constipated and straining on the toilet causes varicose veins”

A.

In the 1960s, there was a movement to suggest that populations that ate a lot of vegetable fibre and roughage did not get varicose veins, whereas Western populations that had low fibre diets and tended to suffer from constipation got varicose veins more often.
 
However population studies performed subsequently showed that this to be wrong. If the age of the population has taken into account, then it was found that there is no real link between a tendency to constipation and the development of leg varicose veins. Of course there may be a link with haemorrhoids (piles) but this is a separate issue, related to the physiology of the veins around the lower gut and the anal canal.
 
As with several of the other incorrect myths above, the thought process behind the blaming of varicose veins on constipation appears to be the idea that increasing pressure on the pelvic veins by straining, causes an increase of pressure in the blood within the pelvic veins, which is then transmitted into the legs causing leg veins to dilate. This does not happen.
 
Pressure on the veins in the pelvis would cause the veins to close and therefore would put the patient at risk of deep vein thrombosis (DVT) in the pelvic veins, but not of varicose veins in the legs. However there is no evidence that constipation or straining on the toilet can actually close the pelvic veins, and there are no reports that people with constipation get pelvic deep vein thrombosis.

Q6 “Hot baths cause varicose veins”

A.

The idea that hot baths can cause varicose veins is an example of the simple sort of thinking that we often see in medicine, where one fact that seems obvious is extrapolated to another situation that appears to be the same, but drawing incorrect conclusions.

In this case, we know that heat causes veins to dilate. We also know that varicose veins are dilated veins. Therefore it would seem logical that the two must be linked.

Of course this is not the case.

When veins dilate due to heat, this is a normal physiological reaction of normal veins in the skin that are concerned with temperature control. Varicose veins however, are pathologically dilated veins, deeper under the skin than the veins involved in temperature control, which dilate because of venous reflux during standing and walking.

Another very simple and obvious argument is: - if hot baths really did cause varicose veins, why is it that people often get varicose veins only on one leg and not the other? And why is it that when we scan patients, it is often only one vein that has lost its valves and become varicose, rather than all of the veins in the leg?

If varicose veins were really caused by having hot baths, then we should see veins affected in both legs in all people, and all of the veins in the legs should be affected. Similarly, if heat is a cause of varicose veins, we really should be seeing large numbers of varicose veins in populations living in hot climates and far fewer in people living in colder climates.

However it is remarkable that when population studies are performed and results are corrected for the age of the population, the number of people with varicose veins and "hidden varicose veins" (venous reflux or venous incompetence) is very similar in similar populations in different countries with vastly different temperatures.

Therefore hot baths and indeed hot weather do cause normal veins to dilate which will shrink again in the cold, but these factors do not cause varicose veins.
 

 
 
This website was last updated on 11/10/16.

 

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